PalmSource Inc.(PSRC), which develops operating system software for handheld computers and phones, on Monday said David Nagel has stepped down as president, chief executive officer and director.

The company, in a statement, gave no reason for Nagel's departure, which was effective on Sunday. PalmSource officials could not be reached immediately for further comment.

PalmSource named Patrick McVeigh, 53, senior vice president, worldwide licensing, as interim CEO while the board searches for a permanent replacement.

Nagel, 60, will stay at PalmSource through mid-July in an advisory role.

Nagel joined Palm Inc. in 2001 to run the handheld computer maker's software unit, which eventually was spun off as PalmSource. Nagel, a former AT&T Corp. (search) chief technology officer, was named PalmSource's CEO later in 2001 and helped take the company public in 2003.

PalmSource's stock has crumbled since its IPO, falling from about $40 a share to its Friday Nasdaq close of $9.01.

PalmSource's software is primarily used in pocket-sized personal digital assistants, or PDAs, whose demand has slowed sharply after dramatic growth only 4 years ago.

The Sunnyvale, California-based company recently has tried to beef up its relationship with makers of mobile phones, including those in international markets.